For the Berlin method of marine filtration to work your tank needs to adhere to certain rules. You should typically use 1 to 2 pounds of live rock to every 4 litres of water in your aquarium.
Anemones are actually animals that attach themselves to corals or even rocks. They have stinging cells and these things can paralyze small sea creatures. This is one good defense mechanism for these little babies. There are others who say that crabs and sea anemones share something close to a symbiotic relationship. This is because crabs will eat the small sea creatures that died from the sting and the anemones will eat the scraps of the crab.